Method and system for precision spheroidisation of graphite

ABSTRACT

A system is disclosed. The system includes an impact processor comprising an inlet and an outlet, a secondary classifier comprising an inlet and an outlet, the secondary classifier being downstream of and coupled to the impact processor, a recirculation mixer valve downstream of and coupled to the outlet of the secondary classifier, and a recirculation line coupling the outlet of the first secondary classifier to the inlet of the impact processor.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.15/596,948, filed on May 16, 2017, which is a non-provisional of, andclaims the benefit of the filing date of U.S. Provisional ApplicationNo. 62/338,046, filed on May 18, 2016, which are herein incorporated byreference in their entirety for all purposes.

SUMMARY

Embodiments of the invention provide for an optimized process forproducing graphitic spherules from natural graphite that, as a productpowder, are typified by favorable properties, not least including asmall standard deviation of particle size distribution, and maximum bulkdensity. In the following, this product may be referred to as HighDensity Natural Spherical Graphite, HDNSG. The HDNSG is furthercharacterized by its high density and homogeneity of the individualspherical particles, as well as its surface-anisotropy represented bythe dominantly tangential orientation of the outer compressed andparticle-embedded graphene layers. These modifications promote theuniformity of the particle's intrinsic lithium ion diffusion properties,as well as enhances low temperature charge and discharge performance,when the particles are present in an anode of a lithium ion battery.

One embodiment of the invention is directed to an impact processorcomprising an inlet and an outlet; a secondary classifier comprising aninlet and an outlet, the secondary classifier being downstream of andcoupled to the impact processor; a recirculation mixer valve downstreamof and coupled to the outlet of the secondary classifier; and arecirculation line coupling the outlet of the first secondary classifierto the inlet of the impact processor.

Another embodiment of the invention is directed to a method forprocessing particles, the method comprising: introducing a fluid streamcomprising particles to an impact processor; milling the graphiteparticles in the impact processor; passing the milled graphite particlesto an inlet of a secondary classifier; separating the milled graphiteparticles in the secondary classifier into a first graphite particlestream and a second graphite particle stream; passing the secondgraphite particle stream to a recirculation mixer valve; andrecirculating at least some of the graphite particles in the secondgraphite particle stream to the inlet of the impact processor via arecirculation line.

These and other embodiments of the invention are described in furtherdetail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-E shows illustrations of a flake re-shaping at different stagesof the transformation process. FIG. 1A shows a sketch of a pure flake ofa given size. In FIG. 1B, the flake has been exposed to substantialimpacts with the processing equipment and other graphite particles. As aresult, the flake starts to bend and partially disintegrate at theedges. In FIG. 1C, processsing has progressed to the degree where moresubstantial defoliation and dislocation of the flake occurs as well asmore substantial bending of these defoliated layers. FIG. 1D shows thefinal product, the approximately spherical, rounded particle resemblingthe appearance of a “brussel sprout” that is created towards the end ofthe process. FIG. 1E shows a “cross-section” through this sprout, with aclearly visible graphite flake core area that remains relativelyunaltered by the impact processing forces.

FIG. 2 shows a graph illustrating the ideal volume of “brussel sprouts”HDNSG spherules with different nominal diameters, assuming an idealsphere or ellipticity of 1.0.

FIG. 3 shows a graph that describes a typical particle size distributionfor HDNSG products, with a nominal particle diameter of D_(N)=23 μm.

FIG. 4 shows a graph illustrating a range of ideal raw flake inputmaterial size distribution as function of product target dimensions,assuming no volumetric loss or gain.

FIG. 5 shows a diagram of an impact classifier processor.

FIG. 6 shows a system including an impact classifier processor, asecondary classifier, and a dust collector.

FIG. 7 shows an example for a chain systems of the type shown in FIG. 6.

FIG. 8 shows an example of a system that may be a first stage of themulti-stage HDSG production process according to an embodiment of theinvention.

FIG. 9 shows a second stage including downstream processing equipmentfor the production of high quality high density natural sphericalgraphite based on classified pre-shaped graphite flake particles.

FIG. 10 shows a combined first and second stages of the HDNSGmanufacturing process.

DETAILED DESCRIPTION

Rechargeable battery systems, i.e. based on lithium ion technology,contain an anode and a cathode. In many applications of such or otherbattery systems, carbon based materials are used for the active materialof the anode.

Conventional carbon-based materials are shaped into smaller diameterspherules for technical and physical reasons, and modification isachieved using various processing equipment and techniques. Thepreferred raw material source for these carbon materials is graphite.Two different versions of graphite are commonly used as startingmaterial. Synthetic graphite, which is derived from refinery or coalbaking residues, and natural graphite, which is mined in amorphous,flake or vein form at various sites globally.

Natural graphite occurs predominantly in amorphous carbon anddisseminated flakes of different size and shape. The term “flake”describes crystalline graphite comprised of highly ordered layers whichultimately defined the size ratio of the particle. In Cartesiancoordinates an idealized three dimensional even particle can bedescribed with by three dimensions: X, Y, Z. A typical flake features asimilar length for two sides, X and Y, with a third side, Z,significantly smaller than X, or Y. Other common flake shapes resemblehexagonal structures or even more complex structures. Typical values forZ range from 0.1X to 0.05X.

Natural graphite flake used for processing into spherical graphite isrepresented in a wide size range, i.e. typically within the −100 Meshfraction, or <149 μm, but also larger flake fractions are commonly used.

The process described herein resembles a physical-mechanical producttransformation from prismatic flake graphite, through crumpled flake,into a characteristically well-rounded ellipsoidal or spherical endproduct, the HDNSG.

One embodiment of the invention is that transformation occurs gradually,across a multi-step process, whereby the degree of the transformationcan be simplified for description as the sum of all milling and shapingimpacts each flake has encountered throughout the duration of the entireproduction process. FIGS. 1A-E illustrates this product transformationprocess at different stages of progression.

FIG. 1A shows a sketch of a pure flake of a given size. In FIG. 1B, theflake has been exposed to substantial impacts with the processingequipment and other graphite particles. As a result, the flake starts tobend and partially disintegrate at the edges. In FIG. 1C, this processhas progressed to the degree where more substantial defoliation anddislocation of the flake occurs as well as more substantial bending ofthese defoliated layers. FIG. 1D shows the final product, theapproximately spherical, rounded particle resembling the appearance of a“brussel sprout” that is created towards the end of the process. FIG. 1Eshows a “cross-section” through this sprout with a clearly visiblegraphite flake core area that remains relatively unaltered by the impactprocessing forces.

With refined graphitic properties and functional characteristics, theHigh Density Natural Spherical Graphite comprises a core surrounded byattached compressed spherically layered surface carbon, where thecrystallinity of the core graphite is more crystalline than the surfacematerial, as defined by spectroscopy or diffraction techniques. Thevariation in crystallinity is caused by the increased extent to whichthe outer layers have been exposed to mechanical impact and shear force,which induces additional microscopic stress and deformation in thisregion and exposes additional edge plane defects.

The difference in graphite lattice composition between core and exteriorof the HDNSG particle, in some embodiments, does not exceed; 15%expansion in basal carbon aromatic layer (d₀₀₂) spacing, as defined byElectron Microscopy or X-Ray Diffraction where the core spacing isbetween 3.35 Å and 3.4 Å, or 0.3 in Raman Spectroscopy Intensity Ratiosbetween the Defect (D1355) and Graphite (G₁₅₈₂) peaks, I_(D)/I_(G),where the graphite core I_(D)/I_(G) Intensity Ratio is between 0 and0.3. The true specific density of the High Density Natural Sphericalgraphite can be about 2.2 t/m³ or greater, and the averaged ellipticityof individual HDNSG particles is between about 0.7 and 1.0. The HDNSGparticle surfaces can be mechanically modified to achieve a microscopicsurface roughness of less than about 15% radial radii distance of therelated nominal particle radius, R_(N). The tap density of the productcan be between about 0.92 t/m³ and 1.34 t/m³ and the nominal BET surfaceis greater than about 2.6 m²/g.

The complete product transformation process, inclusive of alltransformational equipment, machines or apparatuses, can be defined bythe result of the sum of all stochastically relevant impulse transfersonto any graphite particle at any time and location within andthroughout the duration of the entire process.

In some embodiments, the process can involve two interlinked stepsfollowing each other, with an optional intermediate step in between. Thefirst step of the process utilizes equipment and process parameters thatare designed and optimized to modify the input raw material of bulknatural flake graphite into the preferred size or shape fraction ofnatural graphite particles. The preferred size or shape fraction of thenatural graphite particles are used in the second step of the process interms of particle homogeneity and size distribution that leads to theHDNSG, and simultaneously maximizes yield of production.

As described above, the natural flake graphite process input materialtypically has a wide particle size distribution, i.e. usually within the−100 Mesh fraction, or <149 μm, but larger flake size fractions may alsobe used.

For the production of a specific nominal HDNSG fraction, a specificoptimal flake input material can be used. As consequence, a relativelysmall fraction of the wider, raw flake, material concentrated throughmining practice can be directly used and re-shaped into HDNSG. Fractionsthat are too small, e.g., “fine” particles, can be removed, andfractions of particles that are too large, e.g., “jumbo” particles,preferably undergo size reduction. The optimal input size distributionis therefore collected by a primary means of milling, pulverization andsize classification.

Size reduction and classification is one objective of the first processstep in the aforementioned interlinked process. This first process stepuses milling equipment that simultaneously facilitates the removal offine particles, and the rapid extraction of optimally sized particles,before they can be further broken down into fines. Here, the jumboparticles are reliably retained to undergo size reduction until theoptimal size fraction for extraction is achieved.

One objective of the second process step, in the interlinked process, isre-shaping the optimized flake fraction, derived from the first processstep, into HDNSG while minimizing further material loss caused bydestructive milling or abrasive effects.

For the conversion of flake into High Density Natural Spherical Graphite(HDNSG), resembling a “brussel sprout” of a particular nominal idealdiameter D_(N) (i.e. D_(N)=16 μm), a certain nominal volume can bedefined through simplifying the particles' complex geometry to aball-like sphere shape. Hence, as example, the theoretical object volumefor D_(N)=16 μm and D_(N)≤32 μm particles are approximately 2,150 μm³and 6,370 μm³, respectively.

FIG. 2 shows the ideal volume of “brussel sprouts” HDNSG spherules withdifferent nominal diameters, assuming an ideal sphere or ellipticity of1.0.

FIG. 3 shows a typical particle size distribution for HDNSG products,with a nominal particle diameter of D_(N)=23 μm.

Depending on the nominal characterizing dimensions of the HDNSG product,there is an ideal input flake size which directly correlates to thedimensions of the ideal spherule, assuming there is no volumetric lossor gain during the process. FIG. 4 shows a range of ideal raw flakeinput material size distribution as function of product targetdimensions, assuming no volumetric loss or gain.

FIG. 4 assumes that spherical graphite resembling “brussel sprouts” areproduced from prismatic flakes or various forms, square, rectangular andhexagonal, with a nominal thickness, Lc, one fifth of the radius, aspreviously emphasized based on natural flake graphite dimensions. Theparticle transformation process, as shown in FIGS. 1A-E, constitutesdeformation of prismatic particles into re-shaped well-roundedellipsoidal particles by folding, overlapping, compression, andsmoothening, which in this case assumes no material loss.

Inherently, a variable component of material loss occurs throughmilling, as graphite particles are re-sized and shaped through physicalimpact or shear force. For instance, assume that a square particle witha length of 100 μm will pass through 60 μm classification. The particleis cleaved in half twice, and this would create four 50×50 μm particles.In this situation, there is no material loss. However, if the particleis to be broken across an undesirable orientation, within astoichiometric material flow, a significant portion of byproduct fineparticle material will be created.

In embodiments of the invention, to reduce byproduct generation,particles can be cleaved most intensely within the first unit ofequipment, the first of the distinctive process steps, brieflyclassified and retained by means of the internal classifier (ifimplemented), and then sharply classified within an externalclassification unit.

Larger particles then can be recirculated rapidly to minimize the degreeto which shaping impacts can result in fine waste material.

To a lesser extent, the abrasive smoothening component of processing,especially during the second of the distinctive process steps, alsoresults in a volumetric loss to the original particle.

Stochastically, a small amount of this fine material loss fraction, isreintegrated into the larger particle through compression or simply bybeing enclosed inside larger defoliated graphite layers. The extent towhich this is happening depends on the material properties of thegraphite raw material as well as the operative process parameters.

In general, production yields are approximately 40% or greater. Thus, asignificant proportion of the graphite is lost during the re-sizing andabrasive phases collectively.

Depending on initial raw material flake size distribution, the materialloss to occur during abrasive smoothing events is interpreted to be lessthan the re-sizing phase. Consequently, the flakes which undergo bothre-shaping and smoothing are larger than those described in FIG. 4 tocompensate for the material loss. FIG. 4 shows approximately the lowerlimit to prismatic feed material for the second process step, wherebending, folding, defoliation and smoothing occurs.

The typical value for this material loss factor, within the secondprocess step can be between about 0.1-0.3. Classification equipment canthus be calibrated in line with this factor to facilitate the real,inflated, flake size requirements to produce ideal “brussel sprout”spherical graphite.

As a tendency, with increased compaction of the “brussel sprouts”spherical graphite, its volumetric density increases. Therefore, ahighly compacted “brussel sprouts” spherical graphite represents a highquality High Density Natural Spherical Graphite (HDNSG). Typically, thishigh quality, high density spherical product is correlated to largermaterial losses during processing, as improvements to density andsmoothing require an increased duration of impulse and shear exposure.

As FIG. 4 shows, the ideal flake dimensions for the flake to bemodified, re-shaped, into the bespoken spherules of a defined diameter,will likely be smaller than the largest flake sizes of the originalinput (raw flake) material (which can be larger than 150 μm). Onepurpose of the first part of the production process, therefore, is toexpose any of these oversized flakes to a milling event that reduces itsphysical dimensions to the optimal size.

Typically, the ideal range for flakes to be re-shaped into common HDNSGproducts is set between about 30 μ-150 μm, subject to actual flakeshape, material loss fraction and final HDNSG product diameterspecification which typically is in the range of about D_(N)=11μm−D_(N)=23 μm, or beyond.

The conventionally utilized production equipment for the production ofspherical graphite has a number of limitations. Essentially, two typesof equipment and process philosophies are evident in current industrialpractice. The first type of equipment and process is the usage ofseparated dedicated equipment for milling, by exposing the raw flakeinput material to a milling machine, which creates a wide range ofmilled flake particles of which a small fraction is of the right sizedistribution, and with a substantial large fraction being too small anda smaller fraction being too large. This mix of processed flake is thentransferred into a separate machine or apparatus, called a faculty mill,in which the flake mixture is exposed to a batch processing ofspherodisation. Following this batch process, the material is dischargedfrom the faculty mill and subject to a classification treatment. Thisprocess produces a poor quality of spherical-like graphite in thesuitable size range for the final product. However, the final producthas a very low tap density, very inhomogenous particle shapes and a widedistribution of particles, including a large portion of particles thatare too fine and is discharged as waste.

The second type of equipment and process is based on a series of similarsets of equipment and is described as follows. The core of eachprocessing equipment set is a milling systems, commonly an airclassifier mill, shown in FIG. 5, which is combined with aclassification system. FIG. 5 shows a diagram of an air classifier mill.This mill can be generically referred to as an impact classifierprocessor, and further generically as an impact processor.

FIG. 5 shows an air classifier mill that includes a particle feedersystem 1, which may feed particles to an interior of the housing of theimpact classifier processor. The housing may house a rotating impactrotor 2, which may be proximate to stationary impact zone liners 3. Agas inlet 4 may supply a process gas to the interior or the housing. Aflow guide 5 may guide the process gas in the interior of the housing.An internalized rotating classification device 7 may be present insideof the flow guide 5, and gas may be exhausted through the exhaust 7.Impactor heads 8 may be attached to the rotating impact rotor 2. Theimpactor heads 8 and the stationary impact zone liners 3 may form animpact zone 9 where graphite particles are impacted.

Referring to FIG. 5, graphite particles {dot over (M)}_(1,a), are fedinto the particle feeder system 1 from where they are conveyed by meansof a pneumatic air jet (or else) into the milling chamber. Within thischamber, the impact rotor 2 transfers kinetic energy onto the particlesand accelerates them onto a collision course with the liners 3. Duringthis high impact collision, the flakes are predominantly broken, or“milled.” However, especially at lower impact speed and energy, they areshaped into spherules as well.

The process air stream which is flowing into the ACM (air classifiermill) through the gas inlet 4 carries all smaller and lighter particlesupstream within the ACM from where they can be extracted by the airstream through the exhaust outlet 7. In many variants, this ACM has anin-built rotating classification device 5 and 6 which internally rejectscoarse material.

This ACM can be referred to as a classifier impact processor, and canarranged with further equipment, as shown in FIG. 6. FIG. 6 shows adiagram of a conventional system including a classifier impact processor10 (type 1), a secondary classifier 20 downstream of the classifierimpact processor 10 (e.g., type 1), and a dust collector 30 (e.g.type 1) downstream of both.

The classifier (or classification device) 6 in the classifier impactprocessor 10, rejects coarse material from the graphite particles {dotover (M)}_(1,a) fraction, that does not yet satisfy the specific productspecifications for this particular set of equipment in terms of size andshape, and mass. This rejected material will stay inside the classifierimpact processor 10 until further impact processing has resulted insufficient particle modification that allows the particles {dot over(M)}_(I,b) to exit the classifier impact processor via the processgaseous fluid-flow stream. However, due to the strongly irregular shapeof the initial graphite particles, this classification function islimited.

These particles {dot over (M)}_(1,b) are air-conveyed into the secondaryclassifier 20, where a separation of the intended target material {dotover (M)}_(I,c), and the unintended fine waste {dot over (M)}_(I,e)occurs, which at this point is included in the carrier gaseousfluid-flow {dot over (M)}_(I,f), and is represented by the combined massflow {dot over (M)}_(I,d). The unintended fine waste, loss, {dot over(M)}_(I,e), is separated from the carrier gaseous fluid-flow {dot over(M)}_(I,f) by means of a separation unit, i.e. a dust collector 30.

By repetition of this process utilizing a chain of equipment sets, asshown in FIG. 7, the product can eventually be refined from chain stepto chain step, until sufficient combined exposure of the graphitematerial to the combined number of impacting equipment has occurred andthe final product can be discharged.

FIG. 7 shows a diagram of a chain of graphite product transformationequipment. FIG. 7, as an illustrative example, shows only a chain of 3sets of equipment with:

{dot over (M)}_(1,c)={dot over (M)}_(2,a){dot over (M)}_(2,c)={dot over (M)}_(3,a){dot over (M)}_(3,c)={dot over (M)}_(4,a)

{dot over (M)}_(4,c)= . . .

. . . <{dot over (M)}_(4,a)<{dot over (M)}_(3,a)<{dot over(M)}_(2,a)<{dot over (M)}_(1,a)

However, as stated, the length of the chain can be substantially larger.It is also possible to adjust the size of equipment in between sets,with the later sets in the chain being smaller than the earlier one inorder to compensate for the smaller specific mass flow.

A number of improvements to this system can be made that will addressedby embodiments of the invention. First, the illustrated system uses alarge number of equipment sets, as up to 17 or more steps, each equal toone set of equipment, within one chain of equipment. Further, due to thefact that during each step some fine waste material is removed, thelater sets are operating on a lower load point resulting on higherproduction cost. Alternatively, the earlier steps can be operated onhigher throughput rates, which would result in lower quality and wouldrequire compensation by adding more steps, and sets of equipment to thechain of equipment.

As described above, depending on the nominal dimensions of the sphericalgraphite product that is to be produced from the raw flake graphiteinput material, there is an ideal flake size directly correlating withthe dimensions of the ideal HDNSG particle (e.g., FIG. 4).

Embodiments of the invention can focus on two distinctive aspects of theprocess, the optimization of the first process step, the milling, andthe optimization of the second process step, the shaping.

A. Optimization of the First Step (Milling):

FIG. 8 shows an example of a system according to an embodiment of theinvention. The system shown in FIG. 8 may be characterized as a firststage of the multi-stage HDSG production process.

The optimization of the raw flake input material milling process stepcan be achieved by adding and introducing a tight and selectivemulti-classification circuit to the modified milling equipment,including variable partial re-circulation of the ejected, classifiedgraphite particles, as shown in FIG. 8.

FIG. 8 shows an impact processor 10 coupled to and in fluidcommunication with a first secondary classifier 20, a second secondaryclassifier 25, a third secondary classifier 26, and a dust collector 30.The dust collector 30 is furthest downstream from the impact processor10. The impact processor 10 may be a classifier impact processor 10 insome embodiments of the invention. Suitable impact processors mayinclude the type of impact processor shown in FIG. 5. Other types ofimpact processors may include hammer mills, pin mills, and jet mills.

The impact processor 10 comprises a housing and a first inlet 10A, asecond inlet 10B, and an outlet 10C coupled to the housing. The firstinlet 10A is for receiving graphite particles from an upstream graphiteparticle source 130 of graphite particles. The graphite particles fromthe source 130 may pass through a raw flake input material feedercontrol 37. The second inlet 10B is for receiving recirculated graphiteparticles. The outlet 10C is for outputting processed graphiteparticles.

The first, second, and third classifiers 20, 25, 26 (as well as theother classifiers mentioned in this application) may include anysuitable type of apparatus that can separate particles according to sizeranges and can shape particles. Exemplary classifiers may includecyclonic air classifiers, inertial classifiers, and screen classifiers.

The first secondary classifier 20 comprises a housing, and a first inlet20A, a first outlet 20B, and a second outlet 20C coupled to the housing.The first inlet 20A is coupled to the impact processor 10 and is forreceiving processed graphite particles from the outlet 10C of the impactprocessor 10. The first outlet 20B provides a particle stream withparticles {dot over (M)}_(1,c), while the second outlet 20C provides aparticle stream with particles {dot over (M)}_(1,d).

The particle stream with particles {dot over (M)}_(1,c) passes through aconduit to a first recirculation mixer valve 38. The first recirculationmixer valve 38 can pass a graphite particle product stream withparticles {dot over (M)}_(1,p). The graphite particle product streamwith particles {dot over (M)}_(1,p) can then pass to a first downstreamproduct transformation stage 300 (see FIG. 10). Alternatively oradditionally, the first recirculation mixer valve 38 can pass theparticle stream with particles {dot over (M)}_(1,v) back to the inlet10A of the impact processor 10, via a first recirculation line 50.

The second secondary classifier 25 comprises a housing, and a firstinlet 25A, a first outlet 25B, and a second outlet 25C coupled to thehousing. The first inlet 25A is coupled to the second outlet 20C of thefirst secondary classifier 20 and is for receiving processed graphiteparticles from the second outlet 20C of the first secondary classifier20. The first outlet 25B provides a particle stream with particles {dotover (M)}_(1,e), while the second outlet 25C provides a particle streamwith particles {dot over (M)}_(1,f).

The particle stream with particles {dot over (M)}_(1,e) passes through aconduit to a second recirculation mixer valve 39. The secondrecirculation mixer valve 39 can pass a graphite particle product streamwith particles {dot over (M)}_(1,q). The graphite particle productstream with particles {dot over (M)}_(1,q) an then pass to a seconddownstream product transformation stage 302 (see FIG. 10). Alternativelyor additionally, the second recirculation mixer valve 39 can passprocessed graphite particles in a particle stream with particles {dotover (M)}_(1,u) back to the inlet 10A of the impact processor 10, via asecond recirculation line 52.

The third secondary classifier 26 comprises a housing, and a first inlet26A, a first outlet 26B, and a second outlet 26C coupled to the housing.The first inlet 26A is coupled to the second outlet 25C of the secondsecondary classifier 25 and is for receiving processed graphiteparticles from the second outlet 25C of the second secondary classifier25. The first outlet 26B provides a particle stream {dot over(M)}_(1,g), while the second outlet 20C provides a particle stream {dotover (M)}_(1,h).

The particle stream with particles {dot over (M)}_(1,g) passes through aconduit to a third recirculation mixer valve 40. The third recirculationmixer valve 40 can pass a graphite particle product stream withparticles {dot over (M)}_(1,r). The graphite particle product streamwith particles {dot over (M)}_(1,r) can then pass to a third downstreamproduct transformation stage 304 (see FIG. 10). Alternatively oradditionally, the third recirculation mixer valve 40 can pass theprocessed graphite particles {dot over (M)}_(1,u) in a particle streamback to the inlet 10A of the impact processor 10, via a thirdrecirculation line.

The dust collector 30 may comprise a housing and a first inlet 30A, afirst outlet 30B, and a second outlet 30C coupled to the housing. Thesecond outlet of the third secondary classifier 26 can be coupled to andprovide the particle stream with {dot over (M)}_(1,h) to the inlet 30Aof the dust collector 30. The first outlet 30B of the dust collector 30can pass a particle stream with fine dust particles {dot over (M)}_(1,i)out of the system. The second outlet 30C of the dust collector 30 canpass an air stream {dot over (M)}_(1,j) to a process air flow blower fan99. The process air blower fan 99 can pass an air stream {dot over(M)}_(1,j) to a process air flow intake mixer valve 36. The air stream{dot over (M)}_(1,k) may exit the system from the process air flowintake mixer valve 36. A recycled process gas stream {dot over(M)}_(1,m) may pass to a process air flow intake mixer valve 35 and maymix with fresh process gas {dot over (M)}_(1,n) before entering theimpact processor 10 via the second inlet of the impact processor 10.

In embodiments of the invention, the primary raw flake input material,{dot over (M)}_(1,a), can be natural flake graphite of a wide range ofsize and distribution. Preferably, {dot over (M)}_(1,a) can bepre-classified into optimized distribution ranges, i.e. within the range325 MESH-100 MESH, which is equivalent to flake sizes of approximately44 μm-150 μm.

{dot over (M)}_(1,a) may be a fluid stream comprising a gas and graphiteparticles (e.g., natural graphite flakes) and is fed into the classifierimpact processor 10 in a controlled mass flow via the raw flake inputmaterial feeder control 37, while mixed with a variable partialrecirculation flow of the graphite products {dot over (M)}_(1,c), {dotover (M)}_(1,e), {dot over (M)}_(1,g), which are separated from the mainproduct and process gas flow {dot over (M)}_(1,b), by the first, second,and third secondary classifiers 20, 25, 26. In some embodiments, thegraphite products {dot over (M)}_(1,c), {dot over (M)}_(1,e), {dot over(M)}_(1,g) could be the final products, which may be subsequentlysubjected to various chemical or physical processing steps, as describedin U.S. patent application Ser. No. 15/497,583, filed on Apr. 26, 2017,which is assigned to the same assignee as the present application and isherein incorporated by reference in its entirety for all purposes. Inother embodiments, the graphite products {dot over (M)}_(1,c), {dot over(M)}_(1,e), {dot over (M)}_(1,g) could be intermediate products, whichcould be subjected to further refinement as described in further detailbelow.

Due to the described limitations of the internal classification device 6of the classifier impact processor 10, the main product and process gasflow {dot over (M)}_(1,b) contains a broad range of planar flakes andsemi-deformed flakes. In the impact processor 10, any graphite particlesor flakes can be milled.

One alternative embodiment of the invention is the opportunity toeliminate the internal classification device 6 from the classifierimpact processor 10. However, the internal classification device 6 canalso remain in other embodiments. In any case, to satisfy certainprocess requirement of the process described in embodiments of theinvention, the classifier impact processor 10 does not necessarilyrequire the internal classifier, and can also operate as a sole millingimpact processor 10, while the classification is entirely externalizedand performed by utilizing the secondary classification equipment asdescribed for the method of combined external classification and partialproduct re-circulation into the milling classifier impact processor 10.

If an internal classification device 6 is used, then the operatingparameters of the internal classification device 6, such as carrier gasflow, or classifier wheel rotation speed can be set to minimize productlosses by over-milling into ultra-fine graphite particle waste, {dotover (M)}_(1,e), that would eventually be eliminated from the process bythe dust collector 30 and can be disposed of.

The rather wide product particle size distribution curve of the productparticles carried within the main product and process gas flow {dot over(M)}_(1,b), is successively to be classified in the secondary classifierarrangement 20, 25, 26. This secondary classifier arrangement comprisesat least one classifier 20. However, it can include multipleclassification stages such as three classification stages 20, 25, 26.

In embodiments of the invention, there is no limitation on the number ofsequentially arranged secondary classifiers. However, in some cases, notmore than three classification devices may be used, which would besufficient to produce a narrow distribution of classified pre-shapedgraphite flake material for further processing into at least threedifferent HDNSG main products of different nominal diameters, ideallyutilizing shaping equipment according to the previously described steptwo production lines.

These secondary classifiers can either be of the cyclone type asillustrated in the FIG. 8, or any other type, i.e. sieve shakerscreening machine with a set number of different sieves and outlets.Utilizing screening machines can produce sharper and tighter particlesize distributions which may have an advantage for certain HDNSGproducts to be produced from this screened pre-shaped graphite flakematerial. This may include the possibility of “skewing” or cutting ormulti-modal modification of the particle distribution curves byselectively blending of the classified materials.

Once the screened pre-shaped graphite flake material products arereleased from the classification devices, the graphite flake materialproduct flows ({dot over (M)}_(1,c), {dot over (M)}_(1,e), {dot over(M)}_(1,g,) ) can either be used for direct further processing intospecific HDNSG, represented in FIG. 8 by the partial graphite flakematerial product flows {dot over (M)}_(1,p), {dot over (M)}_(1,q), {dotover (M)}_(1,r), or mixed with each other in order to create a specificblend, or partially be re-circulated into the classifier impactprocessor 10 for a second exposure resulting in re-shaping into smallerdiameters. This re-circulate is represented, in FIG. 8, by the partialgraphite flake material product re-circulate flows {dot over (M)}_(1,v),{dot over (M)}_(1,u), {dot over (M)}_(1,t). These flows may be presentin re-circulation lines 50, 52, 54, between the outlets of the secondaryclassifiers 20, 25, 26, and the input of the impact processor 10.

Another feature of embodiments of the invention is the capability tore-circulate the main process gas flow {dot over (M)}_(1,j), whereby{dot over (M)}_(1,j) is composed of a certain fraction of fresh processgas {dot over (M)}_(1,n), and a re-circulate, {dot over (M)}_(1,n). Afraction of {dot over (M)}_(1,j), which is quasi equivalent to fractionof fresh process gas {dot over (M)}_(1,n), can be released from theprocess, {dot over (M)}_(1,k).

The process can be modified by operating more than one impact processorin parallel, with the number Y of parallel operating impact processors,feeding their graphite particle loaded individual process gas flows {dotover (M)}_(I,b), into combined secondary classifier arrangements.

Especially if the impact processor of this first stage is operatingwithout an internal classification device, the process can be modifiedby operating more than one impact processor in series. The number Z canbe the number of serial operating impact processors, with the last onefeeding their graphite particle loaded individual process gas flows {dotover (M)}_(1,b), into combined secondary classifier arrangements.

The classified pre-shaped graphite flake particles, i.e. {dot over(M)}_(1,p), {dot over (M)}_(1,q), {dot over (M)}_(1,r), depending on thenumber of deployed secondary classification devices, is then transferredinto the downstream processing equipment, as described hereafter, withthe downstream processing equipment being optimized for the finalshaping (spheroidisation) of the supplied classified flake fractions(FIG. 9).

B. Optimization of the Second Step (Re-Shaping):

The optimal natural flake graphite intended for the anode material for alithium ion battery comprises regular, evenly sized, and denselycompressed spherical-like graphite particles; a narrow particle sizedistribution; minimized irregularities in individual particle shapeshown as deviation from the ideal spherule shape; and maximizedvolumetric density within individual spherules. However, naturalprismatic flake graphite comprises stacked sheets of small crystallizedgraphene layers, which resemble thin flat plates of graphite material.In order to transform these flakes into spherical graphite, as inembodiments of the invention, mechanical processing by means ofwell-defined impulse transfer is desired. This can be achieved by are-shaping process, as shown in the system illustrated in the diagram inFIG. 9. The re-shaping process can be optimized for the production ofspherical graphite. Ultimately, the spherules resemble the geometry andtextures of “brussel sprouts” with a core of flake graphite, evenlyclasped by compressed flake laminae and graphite layers tightlycompressed, with minimal cavities and void space. This process leads toa High Density Natural Spherical Graphite product: “HDNSG”.

The graphite particle product transformation from the flake to the endproduct, the HDNSG, occurs gradually, across a multi-step re-shapingprocess, whereby the degree of the shape transformation can be describedas the sum of all shaping impacts each flake has encountered throughoutthe duration of the entire product transformation process.

The shaping itself can be influenced by the geometrical equipment (andthroughput) and parameters such as the product transformation chamber,the enclosed applied product shaping head geometry, physical gapsbetween shaping head fingers, or outer geometry of the transformationchamber, the available physical spaces for the graphite material to flowwithin and re-arrange, the transformation chamber filling level withgraphite (the specific load), operating speeds of the impactor headswithin the transformation chamber, gaseous fluid flow through theequipment (carrier flow), additional ballast loading (with inertmaterial or fine off-shavings, production waste material), and theamount of product re-circulation that happens throughout the producttransformation process, etc.

FIG. 9 shows exemplarily four sets of connected equipment in series. Thefour sets of connected equipment can form a downstream producttransformation stage. The classification equipment in a set of equipmentmay include an impact processor, one or more secondary classifiers, andone or more three way valves. Each equipment set may be configured toprocess a certain size range of particles. The equipment sets may bedenoted by different types, which can respectively process differentparticle size ranges. For example, the different types of equipment setsmay be denoted by type 1, type 2, type 3, type 4, type 5, etc. which ahigher number type processes particles within a smaller size range. Thesizes of the particles of each of the particle streams in FIG. 9 andother figures in this application may be denoted as follows:

. . . <{dot over (M)}_(5,p)<{dot over (M)}_(4,p)<{dot over(M)}_(3,p)<{dot over (M)}_(2,p)<{dot over (M)}_(1,p) . . .

Specifically, FIG. 9 shows a first equipment set 202 comprising a type 2(downstream) impact processor 41, a type 2 first secondary classifier80, a second type 2 secondary classifier 81, and a dust collector 31.

The type 2 impact processor 41 comprises a housing and a first inlet41A, a second inlet 41B, and an outlet 41C coupled to the housing. Thefirst inlet 41A is for receiving graphite particles in particle stream{dot over (M)}_(1,p) from FIG. 8. The second inlet 41B is for receivingrecirculated process gas from a process air flow intake mixer valve (notshown) downstream of the process air blower fan 99. The outlet 41C isfor outputting processed graphite particles in a stream {dot over(M)}_(2,b).

The type 2 first secondary classifier 80 comprises a housing, and afirst inlet 80A, a first outlet 80B, and a second outlet 80C coupled tothe housing. The first inlet 80A is coupled to the impact processor 41and is for receiving processed graphite particles from the outlet 41C ofthe impact processor 41. The first outlet 80B provides a particle streamthat passes through a type 1 first three way valve 70, and eventuallymerges into particle stream {dot over (M)}_(2,v), while the secondoutlet 80C provides a particle stream {dot over (M)}_(2,d1).

The type 2 second secondary classifier 81 comprises a housing, and afirst inlet 81A, a first outlet 81B, and a second outlet 81C coupled tothe housing. The first inlet 81A is coupled to the type 2 firstsecondary classifier 80 and is for receiving processed graphiteparticles from the second outlet 80C of the type 2 first secondaryclassifier 80. The first outlet 81B provides a particle stream thatpasses through a type 1 second three way valve 71, and eventually mergesinto particle stream {dot over (M)}_(2,v), while the second outlet 81Cprovides a particle stream {dot over (M)}_(2,d2).

The dust collector 31 may comprise a housing and a first inlet 31A, afirst outlet 31B, and a second outlet 31C coupled to the housing. Thesecond outlet 81C of the type 2 second secondary classifier 81 can becoupled to and provide the particle stream with particles {dot over(M)}_(2,d2) to the inlet 31A of the dust collector 31. The first outlet31B of the dust collector 30 can pass a particle stream with particles{dot over (M)}_(2,i) out of the system. The second outlet 31C of thedust collector 30 can pass a particle stream with particles {dot over(M)}_(2,j) to a process air flow blower fan 99. The process air blowerfan 99A can pass a particle stream with particles {dot over (M)}_(2,j)to a process air flow intake mixer valve (not shown), and then may mixwith fresh process gas before entering the impact processor 41 via thesecond inlet 41B of the impact processor 41 as stream with particles{dot over (M)}_(2,o).

FIG. 9 also shows a second equipment set 204 comprising a type 3(downstream) impact processor 42, a type 3 first secondary classifier82, a type 3 second secondary classifier 83, and a dust collector 31.

The type 3 impact processor 42 comprises a housing and a first inlet42A, a second inlet 42B, and an outlet 42C coupled to the housing. Thefirst inlet 42A is for receiving graphite particles in particle streamwith particles {dot over (M)}_(2,p) from the first outlet 80B of thetype 2 first secondary classifier 80. The second inlet 42B is forreceiving recirculated process gas in stream {dot over (M)}_(3,o) from aprocess air flow intake mixer valve (not shown) downstream of theprocess air blower fan 99B. The outlet 42C is for outputting processedgraphite particles in a stream with particles {dot over (M)}_(3,b).

The type 3 first secondary classifier 82 comprises a housing, and afirst inlet 82A, a first outlet 82B, and a second outlet 82C coupled tothe housing. The first inlet 82A is coupled to the impact processor 42and is for receiving processed graphite particles from the outlet 42C ofthe impact processor 42. The first outlet 82B provides a particle streamthat passes through a type 2 first three way valve 72, and eventuallymerges into particle stream with particles {dot over (M)}_(3,v), whilethe second outlet 82C provides a particle stream with particles {dotover (M)}_(3,d1).

The type 3 second secondary classifier 83 comprises a housing, and afirst inlet 83A, a first outlet 83B, and a second outlet 83C coupled tothe housing. The first inlet 83A is coupled to the type 3 firstsecondary classifier 82 and is for receiving processed graphiteparticles from the second outlet 82C of the type 3 first secondaryclassifier 82. The first outlet 83B provides a particle stream thatpasses through a type 2 second three way valve 72, and eventually mergesinto particle stream with particles {dot over (M)}_(3,v), while thesecond outlet 83C provides a particle stream with particles {dot over(M)}_(3,d2).

The dust collector 31 may comprise a housing and a first inlet 31A, afirst outlet 31B, and a second outlet 31C coupled to the housing. Thesecond outlet 83C of the type 3 second secondary classifier 83 can becoupled to and provide the particle stream with particles {dot over(M)}_(3,d2) to the inlet 31A of the dust collector 31. The first outlet31B of the dust collector 30 can pass a particle stream with fineparticles (e.g., dust) {dot over (M)}_(3,i) out of the system. Thesecond outlet 31C of the dust collector 30 can pass an air stream {dotover (M)}_(3,j) to a process air flow blower fan 99. The process airblower fan 99B can pass the air stream {dot over (M)}_(3,j) to a processair flow intake mixer valve (not shown), and then may mix with freshprocess gas before entering the impact processor 41 via the second inlet41B of the impact processor 41 as stream {dot over (M)}_(3,o).

FIG. 9 also shows a third equipment set 206 comprising a type 4(downstream) impact processor 43, a type 4 first secondary classifier84, a type 4 second secondary classifier 85, and a dust collector 31.

The type 4 impact processor 43 comprises a housing and a first inlet43A, a second inlet 43B, and an outlet 43C coupled to the housing. Thefirst inlet 43A is for receiving graphite particles in particle stream{dot over (M)}_(3,p) from the first outlet 82B of the type 3 firstsecondary classifier 82. The second inlet 42B is for receivingrecirculated process gas in stream {dot over (M)}_(4,o) from a processair flow intake mixer valve (not shown) downstream of the process airblower fan 99C. The outlet 43C is for outputting processed graphiteparticles in a stream {dot over (M)}_(4,b).

The type 4 first secondary classifier 84 comprises a housing, and afirst inlet 84A, a first outlet 84B, and a second outlet 84C coupled tothe housing. The first inlet 84A is coupled to the impact processor 43and is for receiving processed graphite particles from the outlet 43C ofthe impact processor 43. The first outlet 84B provides a particle streamthat passes through a type 3 first three way valve 74, and eventuallymerges into particle stream with particles {dot over (M)}_(4,v), whilethe second outlet 82C provides a particle stream with particles {dotover (M)}_(4,d1).

The type 4 second secondary classifier 85 comprises a housing, and afirst inlet 85A, a first outlet 85B, and a second outlet 85C coupled tothe housing. The first inlet 85A is coupled to the type 4 firstsecondary classifier 84 and is for receiving processed graphiteparticles from the second outlet 84C of the type 4 first secondaryclassifier 84. The first outlet 85B provides a particle stream thatpasses through a type 3 second three way valve 74, and eventually mergesinto particle stream with particles {dot over (M)}_(4,v), while thesecond outlet 85C provides a particle stream with particles {dot over(M)}_(4,d2).

The dust collector 31 may comprise a housing and a first inlet 31A, afirst outlet 31B, and a second outlet 31C coupled to the housing. Thesecond outlet 85C of the type 4 second secondary classifier 85 can becoupled to and provide the particle stream with particles {dot over(M)}_(4,d2) to the inlet 31A of the dust collector 31. The first outlet31B of the dust collector 30 can pass a particle stream {dot over(M)}_(4,i) out of the system. The second outlet 31C of the dustcollector 30 can pass an air stream {dot over (M)}_(4,j) to a processair flow blower fan 99C. The process air blower fan 99C can pass an airstream {dot over (M)}_(4,j) to a process air flow intake mixer valve(not shown), and then may mix with fresh process gas before entering theimpact processor 43 via the second inlet 43B of the impact processor 43as stream {dot over (M)}_(4,o).

FIG. 9 also shows a fourth equipment set 208 comprising a type 5(downstream) impact processor 44, a type 3 first secondary classifier86, a second type 2 secondary classifier 87, and a dust collector 31.

The type 5 impact processor 44 comprises a housing and a first inlet44A, a second inlet 44B, and an outlet 44C coupled to the housing. Thefirst inlet 44A is for receiving graphite particles in particle stream{dot over (M)}_(4,p) from the first outlet 86B of the type 4 firstsecondary classifier 84. The second inlet 44B is for receivingrecirculated process gas in stream {dot over (M)}_(5,o) from a processair flow intake mixer valve (not shown) downstream of the process airblower fan 99D. The outlet 44C is for outputting processed graphiteparticles in a stream {dot over (M)}_(5,b).

The type 5 first secondary classifier 86 comprises a housing, and afirst inlet 86A, a first outlet 86B, and a second outlet 86C coupled tothe housing. The first inlet 86A is coupled to the impact processor 44and is for receiving processed graphite particles from the outlet 44C ofthe impact processor 44. The first outlet 86B provides a particle streamthat passes through a type 4 first three way valve 76, and eventuallymerges into particle stream with particles {dot over (M)}_(5,v), whilethe second outlet 84C provides a particle stream with particles {dotover (M)}_(5,d1).

The type 5 second secondary classifier 87 comprises a housing, and afirst inlet 87A, a first outlet 87B, and a second outlet 87C coupled tothe housing. The first inlet 87A is coupled to the type 5 firstsecondary classifier 86 and is for receiving processed graphiteparticles from the second outlet 86C of the type 5 first secondaryclassifier 86. The first outlet 86B provides a particle stream thatpasses through a type 5 second three way valve 77, and eventually mergesinto particle stream with particles {dot over (M)}_(5,v), while thesecond outlet 87C provides a particle stream with particles {dot over(M)}_(5,d2).

The dust collector 31 may comprise a housing and a first inlet 31A, afirst outlet 31B, and a second outlet 31C coupled to the housing. Thesecond outlet 87C of the type 5 second secondary classifier 87 can becoupled to and provide the particle stream with particles {dot over(M)}_(5,d2) to the inlet 31A of the dust collector 31. The first outlet31B of the dust collector 30 can pass a particle stream with fineparticles (e.g., dust) {dot over (M)}_(5,j) out of the system. Thesecond outlet 31C of the dust collector 30 can pass an air stream {dotover (M)}_(5,j) to a process air flow blower fan 99C. The process airblower fan 99C can pass the air stream {dot over (M)}_(5,j) to a processair flow intake mixer valve (not shown), and then may mix with freshprocess gas before entering the impact processor 43 via the second inlet43B of the impact processor 43 as stream {dot over (M)}_(5,o).

Embodiments of the invention can optimize the product transformationprocess that, in both stage-individually and in total (e.g., all stagesin series), the amount of the graphite material loss (Σ{dot over(M)}_(I,i)) due to secondary effects is minimized, as input material istransferred into HDNSG of pre-defined particle shape and sizedistribution.

Generally, the larger the size of the initial flake input material inrelation to the size of the final HDNSG product particle size, thesmaller the final HDNSG particle size, and the tighter the target HDSGproduct particle size distribution, the more physical impactmanipulation to the graphite particle. Thus, exposure of the graphiteparticles to the classifier impact processors is needed, and ischaracterized as accumulated impact processing time or exposure.

This can be achieved in at least two ways. First, the number I of stagesthat are interconnected in series can be increased, and second, theamount of stage-internal graphite particle material re-circulation {dotover (M)}_(I,v), can be increased. Typically, the number I of in seriesinterconnected stages can be between about 3 and about 25. In oneembodiment this innovative line of product transformation equipmentincludes a total number of stages I=4, in another I=6, and further I<10.

Due to the gradational variation in graphite particle mass throughput(graphite load point) from previous stage to following stage (in primarygraphite particle mass intake, graphite particle mass re-circulation,particle sizes and shapes), each stage operates on stage-specificparameters regarding gaseous fluid mass-flow, graphite particlemass-flows, impactor and classifier speeds. It is also possible to useimpactors and classifiers with different chamber volumes and geometries.

The sizing and shaping effects on the graphite particle can be describedas the result of the sum (vector addition) of all energy (impulse|vector|) transfer a particle encounters over the course of itsprogression throughout the entire processing stream of stages.

With an increasing amount of accumulated mechanical impulse energytransfer, equivalent to an increased number of encountered impulsetransfers, the geometrical modification of the graphite particleprogresses toward an ideal shape and density for the HDNSG. Beyond acritical threshold of energy transferred, the particle may encounterdestruction due to breaking or abrasive shaving of the surface.

For stationary or quasi-stationary operating conditions, such as a givengraphite particle mass-flow through any impact processor of any stage inthe series of stages of processing equipment, the average impactprocessing time for the individual particle is defined by the individualparticle size in relation to the internal classifier classificationparameter settings, as well as the proportion of material recirculation,etc.

Statistically, for a given particle size distribution of a stagespecific input material {dot over (M)}_(I,p), the likelihood to becarried out of the classifier impact processor within the mass flow {dotover (M)}_(I,b), is increased with reduced mass or diameter forsymmetric spherical like particles as well as for larger andgeometrically highly asymmetrical flake particles, and for the finewaste material that is created during the impact process.

These particles are carried out of the impact processor by the particleand carrier gas flow {dot over (M)}_(I,b), and fed through the secondaryclassification devices (e.g., 80, 81). The first of the secondaryclassification devices (e.g., 80) can be designed and calibrated toremove larger and geometrically highly asymmetrical flake particles,which, by means of the three way valve (i.e. 70) can be introduced intothe re-circulation mass flow {dot over (M)}_(I,v), and can be returnedinto the impact processor for a further round of impact processing.

The second of the secondary classification devices (e.g., 81) isaccepting the overflow of the first classifier and is designed andcalibrated to remove the more processed symmetric spherical likeparticles, which, via forwarding mass flow {dot over (M)}_(I,p), areeither removed from the stage and transferred to a further downstreamprocessing stage, or likewise can be, in any proportion, re-circulatedinto the impact processor, by means of the three way valve (e.g., 71).The dust collector (e.g., bag filter) 31 will remove the fine wastestill carried within the carrier gas flow.

The calibration settings of the separation defining parameters of theimpact processor internal classifier in relation to the first and secondsecondary classification devices can determine the internal throughputof graphite particles through the stage.

The total net throughput through the entire stage can be defined by thestage-internal re-circulation of graphite particles that have beenseparated in the first and/or second classifier of the secondaryclassification devices as well as the production yield of the stage(loss of fine waste material).

A faster throughput (increased graphite mass-net-flow) of graphitematerial through a stage, as well as a reduced re-circulation ofgraphite material within a stage, reduces the average individualgraphite particle exposure time per stage. This results in higherproduction rate. However, it likewise produces a diminishing number oftransferred impulses along the series and a lower cumulative energytransfer per particle within each individual stage.

An increased and faster material throughput will also lead to areduction in effective shape transformation from flake toward HDNSGwithin the particular stage. In order to compensate for the reduction instage-specific impulse energy transfer, the total number of stages,which the graphite material must pass through, can be increasedaccordingly, and vice-versa.

With each progressing downstream stage number, each stage proceeds frominitial shaping towards final precision formation and shaping, andvolumetric compaction of the HDNSG into the characteristic shapesresembling “brussel sprouts.” Thus, impact processor internal agitationsettings and design parameters such as rotating speeds, and impactorgeometry are adjusted accordingly. Impact speed is reduced and impactorgeometry is “rounded”.

The stages, including the impactor processors and classificationdevices, can be calibrated and operated to ensure that graphiteparticles are rolled repeatedly into “brussel sprouts,” where all edgesof the spherical graphite particle are compressed back into thespherical graphite particle form, covered in basal layers, andsmoothened by gentle abrasion.

Minor size reduction due to fractional milling takes place predominantlybecause of the abrasion related to the relative movement of particlesagainst each other and the impactor equipment during the formationprocess.

FIG. 10 shows a diagram of combined first and second stages of the HDNSGmanufacturing process. More specifically, FIG. 10 shows exemplarily thecombination of the first and second stages, as shown in FIG. 8 and FIG.9, comprising a first pulverization and classification stage with threeselective product outlets ({dot over (M)}_(1,p), {dot over (M)}_(1,q),{dot over (M)}_(1,r)) that feed into ({dot over (M)}_(2,p), {dot over(M)}_(3,p), {dot over (M)}_(4,p)) the downstream second stage processingequipment for the production of high quality High Density NaturalSpherical Graphite. In FIG. 10, the downstream equipment is exemplarilyillustrated as a stage-internally recirculating process comprising atotal of 4 internal stages. This number can vary with productrequirements.

Each of 300, 302, 303 may receive graphite particles from the first,second and third secondary classifiers 20, 25, 26, and may becharacterized as first, second, and third downstream producttransformation stages. Each of the first, second, and third downstreamproduct transformation stages 300, 302, 303 may include a number of setsof processing equipment. The first downstream product transformationstage 300 was described with respect to FIG. 9, and the second and thirddownstream product transformation stages 302, 304 may operate in asimilar or different manner than the stage 300, but would be adjusted toaccommodate the different sized particles coming from the secondsecondary classifier 25 and the third secondary classifier 26.

The above description is illustrative and is not restrictive. Manyvariations of the invention may become apparent to those skilled in theart upon review of the disclosure. The scope of the invention can,therefore, be determined not with reference to the above description,but instead can be determined with reference to the pending claims alongwith their full scope or equivalents.

One or more features from any embodiment may be combined with one ormore features of any other embodiment without departing from the scopeof the invention.

A recitation of “a”, “an” or “the” is intended to mean “one or more”unless specifically indicated to the contrary.

All patents, patent applications, publications, and descriptionsmentioned above are herein incorporated by reference in their entiretyfor all purposes. None is admitted to be prior art.

1. A system comprising: an impact processor comprising an inlet and anoutlet; a secondary classifier comprising an inlet and an outlet, thesecondary classifier being downstream of and coupled to the impactprocessor; a recirculation mixer valve downstream of and coupled to theoutlet of the secondary classifier; and a recirculation line couplingthe outlet of the secondary classifier to the inlet of the impactprocessor.
 2. The system of claim 1, wherein the secondary classifier isa first secondary classifier, the recirculation mixer valve is a firstrecirculation mixer valve, and the recirculation line is a firstrecirculation line, and wherein the system further comprises: a secondsecondary classifier comprising an inlet and an outlet, the secondsecondary classifier being downstream of and coupled to the firstsecondary classifier; a second recirculation mixer valve downstream ofand coupled to the outlet of the second secondary classifier; and asecond recirculation line coupling the outlet of the second secondaryclassifier to the inlet of the impact processor.
 3. The system of claim2, further comprising: a third secondary classifier comprising an inletand an outlet, the third secondary classifier being downstream of andcoupled to the second secondary classifier; a third recirculation mixervalve downstream of and coupled to the outlet of the second secondaryclassifier; and a third recirculation line coupling the outlet of thesecond secondary classifier to the inlet of the impact processor.
 4. Thesystem of claim 3, further comprising: a dust collector coupled to anddownstream of the second secondary classifier.
 5. The system of claim 4,wherein the impact processor is an impact classifier processor.
 6. Thesystem of claim 4, further comprising: a graphite particle sourceupstream of and coupled to the inlet of the impact processor.
 7. Thesystem of claim 4, further comprising: a first downstream producttransformation stage coupled to the outlet of the first secondaryclassifier; a second downstream product transformation stage coupled tothe outlet of the second secondary classifier; and a third downstreamproduct transformation stage coupled to the outlet of the thirdsecondary classifier.
 8. The system of claim 7, wherein each of thefirst, second, and third downstream product transformation stagescomprises a downstream impact processor, a downstream secondaryclassifier, and a downstream dust collector.
 9. The system of claim 7,wherein each of the first, second, and third downstream producttransformation stages comprises a downstream impact processor, at leasttwo downstream secondary classifiers, and a downstream dust collector.10. The system of claim 7, wherein each of the first, second, and thirddownstream product transformation stages comprises multiple sets ofequipment, each set including a downstream impact processor, adownstream secondary classifier, and a downstream dust collector.11.-20. (canceled)